Advanced Rendering Techniques and Technologies in Computer Graphics
Explore the world of advanced rendering techniques and technologies in computer graphics, including shading, displacement, surface lighting, volume imaging, and more. Learn about the evolution of RenderMan, GPU applications, real-time vs. non-real-time rendering, and the historical development of rendering methods. Dive into GLSL and HLSL languages for vertex, geometry, and pixel shaders, uncovering the complexities of image synthesis and computation in graphics rendering.
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Presentation Transcript
Shading CMSC 435/634
RenderMan Displacement Surface Light Volume Imager
Displacement Given Position Normal Compute Position Normal Displacement Surface Light Volume Imager
Surface color Given Position Compute Color Opacity Displacement Surface Light Volume Imager
Lighting Given Surface Position Compute Light Direction Light Color Displacement Light Surface Volume Imager
Volume Effects Given Position Color Compute New Color Displacement Surface Light Volume Imager
Image Effects Given Pixel Color Compute Pixel Color Displacement Surface Light Volume Imager
Non-real time vs. Real-time RenderMan GPU Application Application Texture/ Buffer Displacement Vertex Surface Light Geometry Volume Imager Fragment Displayed Pixels Displayed Pixels
RenderMan vs. GPU RenderMan Developed from General CPU code Seconds to hours per frame 1000s of lines Unlimited computation, texture, memory, GPU Developed from fixed- function hardware Tens of frames per second 1000s of instructions Limited computation, texture, memory,
History (not real-time) Testbed [Whitted and Weimer 1981] Shade Trees [Cook 1984] Image Synthesizer [Perlin 1985] RenderMan [Hanrahan and Lawson 1990]
History (real-time) Custom HW [Olano and Lastra 1998] Multi-pass standard HW [Peercy, Olano, Airey and Ungar 2000] Register combiners [NVIDIA 2000] Vertex programs [Lindholm et al. 2001] Compiling to mixed HW [Proudfoot et al. 2001] Fragment programs Standardized languages Compute
GLSL / HLSL Vertex, Geometry & Fragment/Pixel C-like, if/while/for Structs & arrays Float + small vector and matrix vec2, vec3, vec4, mat2, mat3, mat4 Swizzle & mask (a.xyz = b.xxw)
GLSL / HLSL Common math & shading functions Trigonometric, exponential, min, max, abs, length, distance, normalize, dot, cross mix(a, b, t) clamp(t, a, b) step(a, t), smoothstep(a, b, t) reflect, refract
Shader Debugging Render as color Map intermediate values to 0-1 Interpret results Hot reloading Make changes without changing viewpoint Remap debug values vec4(-sign(x), sign(x), abs(x), 1) x / (1 + abs(x)) External debugging tools
Vertex Demo: Blend Positions
Vertex + Fragment Demo: Fresnel Environment Map
Shading Methods Repeating Patterns mod, sin Divide and floor Shapes Implicit form: is this pixel inside Color tables Noise or computed patterns 17
Brick Demo mortar brick gap height width gap
Noise Controlled, repeatable randomness Still spotty GPU implementation Can use texture or compute
Noise Characteristics Repeatable Locally continuous but distant points uncorrelated Values RenderMan [0,1], average 0.5 Perlin s [-1,1], average 0 1/2 1 cycle per unit Versions for 1D-4D input
Noise Subtleties Many noise functions based on a lattice Piecewise function between integer coordinates Hash of integer coordinates control points Interpolating values easy but poor Even with higher-order interpolation Perlin s noise Passes through 0 at each integer Hash gives gradient
Perlin Noise in RenderMan Ci = float noise(floor(1/t)*P); 1 2 3 4 56 7 8 9 12 13 14 15 16 20 22
Fractional Brownian Motion (fBm) // Combine octaves, scaled by 1/f for(f=1; f<=floor(1/t); f*=2) Ci += (float noise(f*P)-.5)/f; Ci += .5; 1 2 3 4 56 7 8 9 12 13 14 15 16 20 23
Turbulence // fBm using abs(noise) for(f=1; f<=floor(1/t); f*=2) Ci += abs(float noise(f*P)-.5)/f; Ci += .5; 1 2 3 4 56 7 8 9 12 13 14 15 16 20 24
Advanced Shading Methods Perturbed patterns Adjust position, radius, etc. with noise Bombing Divide space into cells Compute random position in each cell Check if pixel is inside shape Blending Fade effects in and out with smoothstep
